Liquid hydrocarbon fuel burning engines are used in a wide variety of applications including automotive, transportation, marine, electricity generation and compressors. Such engines are often relatively inefficient and may emit significant quantities of pollutant gases and particles. This is of particular concern when the engines are used in built up areas, e.g. cities where the resultant pollution affects significant numbers of people, but is also of significant concern in other situations.
Liquid hydrocarbon fuels typically include a number of additives to improve the efficiency of combustion, reduce pollutant levels, modify combustion characteristics of the fuel and maintain engine cleanliness (i.e., through use of dispersants and detergents).
Additives which can reduce friction levels or otherwise improve efficiency in an engine are of particular interest as they can improve fuel economy. It is sufficient to say that even a small improvement in fuel economy would have massive impact on a global scale.
Alkanolamide based friction modifiers are one family of chemicals which have been identified to provide significant utility as a fuel additive or as a lubricating oil additive. Alkanolamides are formed by the reaction of fatty acids and/or their esters with diethanolamine (DEA). However, there is a significant problem with existing methods of manufacture of alkanolamides and the by-products formed thereby. It has been found that by-products are prone to form throughout the reaction process. A particularly troublesome impurity formed in the course of this reaction is bis-hydroxyethyl piperazine (BHEP). This has significant implications in that, when the composition is used as a fuel additive, BHEP may block fuel inlets or cause other undesirable build ups in the engine.
Additionally, problems exist in the manufacture of alkanolamides in that significant levels of unreacted fatty acids and/or esters and DEA remain in the final product. It has been well documented that amines can wreak havoc on fluorocarbon based elastomer seals. In this regard, if the amount of unreacted DEA could be reduced, a benefit in engine efficiency could be realized.
The reaction scheme below is a typical synthetic procedure for making diethanol amide.
The procedure involves reacting fatty acid methyl ester with diethanol amine under high temperatures, i.e. 150° C. The drawback of the procedure is that the product is equilibrium between the diethanol amide and ester amine. Prolonged reaction will not drive the reaction to a state where most of the product is diethanol amide which is the desired product. Rather, the equilibrium state stays relatively unchanged at an unfavorable level. Ester amine causes harm issues and is unstable and labile for hydrolysis and formation of non-active species. On the other hand, in the product, there is about 4-7% diethanol amine left over in the product. This is capable of causing corrosion and other harm issues.
Production by industrial scale has proven that even after prolonged reaction time, i.e. 5 hours, the diethanol amide and ester amine ratio is still unsatisfactory. This is reflected by a low amide to ester IR ratio of approximately 2. It typically takes another 3 months “aging” at room temperature for the product to equilibrate to an amide to ester ratio of 3.8 while reducing the DEA content to about 1.5% level.
Herein, we report a process which can quickly shorten the “aging” process for diethanol amide synthesis from several months to a few days. The diethanol amide product has reduced residual diethanol amine content, and the product has the added benefit of less harm issues.
In general, the following patent art teaches elements of the proposed invention, but none are capable of producing an alkanolamide which contains a reduced amount of DEA and BHEP, and in which the diethanol amide to ester ratio in the finished product is increased.
US patent application number US 20080072477 discloses an alkanolamide composition as fuel additive for gasoline grade fuel and liquid hydrocarbon fuel and friction modifying additive which contains a fatty acid and diethanolamine, which contains a specified concentration of bis-hydroxyethyl piperazine. Controlling the rate of addition of diethanolamine and other reaction parameters contribute to a reduction in formation of bis-hydroxyethyl piperazine.
U.S. Pat. No. 4,085,126 discloses fatty alkanol-amide detergent compositions prepared by alkoxylation of a fatty acid followed by transesterification with alkanolamine.
WO 2009050256 discloses a fuel additive for additive package obtained by reacting carboxylic acid compound with alkanol amine under reaction conditions supporting formation of fuel additive containing polysubstituted alkanol amine derivative.
US patent application number US 20050107623 discloses production of hydroxyalkyl amide as friction modifiers for fuel in automotive industry involves reacting primary and secondary alkanolamine with ester optionally in presence of catalyst and in presence of metal silicate.
US 20050097813 teaches a method of purification of hydroxyalkyl amide composition from alkanolamine and ester and/or fatty natural material involves adding non-polar solvent; heating to extraction temperature; adding aqueous salt solution; and separating organic phase.
U.S. Pat. No. 4,729,769 discloses a motor fuel composition containing a detergent additive reaction product of a fatty acid ester and a hydroxy hydrocarbyl amine. JP 08198830 teaches fatty acid diethanolamide-type surfactant preparation with low diethanolamine content by reacting diethanolamine with a fatty acid or its ester or glyceride and subjecting to reverse osmosis.
US patent application number US 20100132253 teaches a fuel additive useful for providing friction modification in internal combustion engine with a friction modifying amount of alkanolamide, where the additive is free of esters or specific molar ratio of amides to esters within additive.
It is therefore desirable for a process of making alkanolamides wherein the “aging” time is reduced and the diethanol amide to ester ratio in the finished product is increased. Further, it is desirable to provide an additive composition comprising an alkanolamide which contains a reduced amount of DEA and BHEP, and which is suitable for use as a liquid hydrocarbon fuel additive or a lubricating oil additive.